The present invention relates, in general, to transportation systems for passengers and cargo, and more particularly, relates to moderate velocity, mass transit systems of the type commonly referred to as "people mover" systems, such as are used in airports, shopping centers, amusement parks.
Existing systems for conveying passengers and cargo over a horizontal course of moderate length at moderate speeds have ranged from moving belts or walkways, common in airports, to monorail trains, found in amusement parks, to cable driven aerial tramways, common to ski resorts, to bus or light-rail trolley systems. Each one of these transportation or people mover systems has been found to have advantages which makes its use particularly suitable for certain applications. There still exists, however, a considerable cost effectiveness gap in people mover transportations systems between the moving beltway and complex, high-technology monorail systems.
At most airports, for example, there is a substantial problem in the transport of passengers between the terminals and parking areas. A similar transportation problem exists in connection with the transport of people between stores and parking areas in large shopping centers. Moreover, the distances between parking areas and aerial tramways is often longer than is desirable in large ski resorts. In connection with the transport of freight or cargo, cargo container depots often have a transportation problem between the crane, which is loading and unloading the containers, and the storage yard.
One of the major disadvantages of the monorail type of people mover system is that the train or vehicle which rides on the monorail is usually relatively heavy because the motor which drives the system is carried by the vehicle, the train. Thus, monorail systems usually require pylons or piers which are substantial in size and spaced relatively close together to support the weight of the train. Installation of a monorail people mover system, therefore, can be very expensive, particularly when there are existing structures around which the monorail must operate. A monorail system presently being installed in a major United States city initally had an estimated cost of 45 million dollars per mile. Construction of a three mile system was started in 1983 and will not be completed until 1986, and the current estimate is that the cost of this monorail system will be approximately 75 million dollars per mile.
Moving beltways are, of course, much less costly than a monorail mass transit system, but they inherently must be operated at relatively slow speeds, e.g., 2-3 miles per hour. Moving walkway systems are particularly well suited for short distances in indoor settings, but their speed and distance limitations often result in users walking next to the beltway, rather than on it.
The principal mass transit system which currently fills the gap between beltways and monorail systems is the use of buses. It is typical at most airport installations to provide a pluralty of mini-stations or waiting areas at the terminal and throughout remote parking areas. A fleet of buses constantly circulates between these stations on a fixed route with the passengers selecting the closest stations to their respective ultimate destinations. Such systems, however, require a plurality of operators, namely, bus drivers, as well as being limited to transport over existing or specially built roadways. Bus-based mass transport systems also tend to have insufficient capacity at peak times and undesirably high capacity during most of the rest of the time.
Another approach to the mid-distance, moderate velocity, people moving problem has been light-rail train or trolley systems. Such people movers usually have an advantage over monorail systems in that the they employ a plurality of cars or vehicles which are much lighter in weight than a single monorail train. Accordingly, the supporting track does not have the same costly support requirements that are present in monorail systems. Light rail trains or trolleys, however, have many of the disadvantages of bus-based systems in terms of the need for operators or an automatic control system. Moreover, light-rail trains also are faced with space problems in connection with obtaining right of ways for their track, particularly when the systems are retrofitted to existing structures, roadways, etc.
Automated light-rail trains inherently have control system problems and costs which increase in proportion to the number of passenger carrier cars in the system. Thus, at least some of the monorail cost savings achieved by lighter transport cars is given back in light-rail systems to operators or automatic controls.
Aerial tramways have been employed to a limited degree as general purpose people mover systems, but their use has largely been relegated to mountainous terrain and particularly ski resorts. Rope-based aerial tramways are faced with the problem of having to detach the cabins or cars to stop individual cars while the rope moves. Still further, rope-based aerial tramways are not particlarly well suited for a course in which there are horizontal curves, that is, they can go over existing structures but not easily around them. Additionally, rope tension increases with each cabin added to the system.
Other attempts to fill the gap between monorail train systems and moving walkways can be found in the patent art. Thus, in U.S. Pat. No. 3,690,266 a monorail system is disclosed in which a powered car or passenger carrier unit is suspended from beneath the monorail. In U.S. Pat. No. 3,735,710 a passive or unpowered passenger carrier unit is propelled along a track by a plurality of drive wheels which engage both sides of the vehicle to sequentially advance the passenger carrier unit along the track. Similarly in the system disclosed in U.S. Pat. No. 3,903,807, a plurality of drive wheels are positioned underneath a passive passenger carrier vehicle so as to sequentially drive the vehicle along a path of drive units. In U.S. Pat. No. 4,503,778, unpowered vehicles are supported from a track and then propelled by drive wheels which positioned proximate the track engage a rail or keel beneath the vehicle. U.S. Pat. No. 3,039,402 discloses a powered wheel which is positioned proximate a railroad track is used to drive railroad cars during switching operations.
Such prior patented people mover systems, however, generally have not been commercially exploited to any significant degree. They inherently include certain disadvantages in construction or operation. Thus, some of the systems are undesirably complex, others require bulky track or rail structures, and still others are powered inefficiently.
Accordingly, a gap in moderate velocity, moderate distance, people mover systems still remains between a monorail or light-rail trains and moving walkways.